Electric motor.



A. G. EASTWOOD.

ELECTRIC MOTOR.

PATENTED APR. 7, 1903.

APPLICATION FILED JAN. 15. 1903.

H0 MODEL.

Mam

UNITED STATES PATENT OFFICE.

ARTHUR O. EASTWOOD, OF CLEVELAND, OHIO.

ELECTRIC MOTOR.

SPECIFICATION forming part of Letters Patent No. 724,827, dated April 7,1903.

Application filed January 16, 1903. Serial No, 139,145. (No model.)

To all whom, it may concern:

Beitknown that I, ARTHUR O. EASTWOOD,a citizen of the United States, anda resident; of Cleveland, Ohio, have invented certain Improvements inElectric Motors, of which the following is a specification.

My invention consists of an improved electric motor and apparatus forcontrolling the same, having for its object the provision of aconstruction such that it is possible to start and operate the motor atany desired speed without requiring or utilizing resistance A furtherobject of the invention is' to so construct the motor that it shall bepossible to safely and elficiently apply current at full- 7 line voltagedirectly to it even though said motor be attached to a load, it beingfurther desired to provide a construction possessing the above-notedadvantages which shall be applicable to all types of motors regardlessof Whether they are designed for alternating or direct current work.

The apparatus at present in use for the purpose of controllingdirect-current variablespeed motors necessarily includes resistancesubdivided into a number of sections,depending upon the number of speedsdesired, and is open to the objection that not only is the number ofattainable speeds limited by the number of subdivisions of theresistance, but this number can only be increased by excessivecomplication of parts, and consequently greatly-increased expense. Aswill be appreciated by those skilled in the art, there is always underoperating conditions more or less destructive arcing occurring betweenthe contact elements of the controlling device, in addition to whichthere is a rapid deterioration of the resistance material, due to thealternate heating and cooling to which it is subjected in regulating thecurrent both in starting and in the operation of the motor. Further,owing to low armature resistance an excessive and frequently injuriousrush of current invariably takes place when the motor is started fromrest, this being particularly serious when it is endeavored to start themotor under load. The speed of an induction alternating-current motor,on the other hand, is at present controlled either by inserting atransformer in series with the primary of the motor and varying thenumber of eifective turns in said transformer, so as to vary the voltagesupplied to the motor, or by inserting a variable resistance in serieswith the secondary of the motor.

All of the above-mentioned apparatus has,

in addition to the objections noted, disadvantageous and inefficientfeatures inherently connected with it, all of which are obviated in myimproved electric motor. The above-noted objects and advantages I attainas hereinafter set forth, reference being had to the accompanyingdrawings, in which Figure 1 is an end elevation of a motor and itscontrolling mechanism constructed according to my invention; and Fig. 2is a side elevation of the motor shown in Fig. 1, further illustratingthe arrangement of its parts.

In the drawings, A represents the supporting-frame of an electricmotor,having at each end an upwardly-projecting standard a, providedwith bearings for the reception of extensions from the field frame orbody B of the motor, said extensions being in the present instance madetubular for the accommodation of a shaft 0, upon which is carried thearmature O of the motor. (Indicated in dotted lines in Fig. 2.) Thefield-frame B is thus supported so as to be free to revolve, as is alsothe armature O, the interior of the tubular extensions 19 serving asbearings for the, armature-shaft, which is provided at one end with apinion 0, whereby any desired form of mechanism may be operated. Saidfield-frame of the motor is provided with a braking-surface 1), uponwhich bear brakeshoes b carried on bars or arms 6 pivoted at b to thesupporting-frame of the device.

'Pivoted to the upper ends of the arms 19 are two links 17 and b alsopivotally connected together, the latter of said links having pivoted toit a third link 12 An operating-arm b is pivoted to any suitable supportat I)", being connected to the link I) and having contact-pieces bplaced to cooperate with two sets of contact-segments d and (1. Carriedby the field-frame B of the motor and suitably insulated therefrom aretwo sets of metallic rings 0 and 0 certain of these being electricallyconnected with the field-windings of the motor, while others areconnected to brush-holders, shown in dotted lines at 0 whereby currentis supplied to the armature 0, it being of course understood that thisconstruction may be modified to suit various forms of motorsas, forexample, in the case of induction-motors, which require no brushes orcommutator.

Brushes c suitably insulated from each other and carried upon arms 0,supported from the standards a, serve to transmit electric current tothe rings 0 and 0 while the contact-pieces d and d are connected to asource of supply of current and to the contact-brushes c in the mannerwell known to the art, the wiring being so arranged that in the deviceillustrated current will be delivered to the motor to turn the pinion cin one direction when the operating-arm Z9 is moved so that itscontact-pieces Z7 engage the segments d and to turn said pinion in anopposite direction when said contacts are moved into engagement with thesegments d.

In operation as soon as the contact-pieces h strike the segments 61, forexample, current is supplied to the motor, and, assuming that a load isconnected to whatever mechanism engages the pinion c, the fieldframe ofthe motor will almost instantly begin to revolve, attaining the criticalor no-load speed of the motor in a relatively very short time. As,however, the operating-arm c is moved upon the contact-segments fartheraway from its vertical position, the system of levers b b b and b isbrought into action and the braking-shoes b are pressed against thebrakingsurface I) of the motor field-frame, thereby tending to stop itsrevolution, said action being assisted, if preferred, by means of aspring I), uniting the two bars b and tending to always draw themtogether. Since, however, there must be as long as current is suppliedto the motor a certain relative angular difierence of speed between thefield of the motor and its armature, said armature will now begin torotate with a velocity depending upon the falling off in the speed ofthe rotating field-frame, and as the arm 13 is moved farther from itscentral position and the braking-shoes b are made to press more stronglyupon the braking-surface the armature will gradually be speeded up untilit finally turns at the full-load speed of the motor.

It will be seen that by the means above described the starting-currentrequired for the motor is reduced to a minimum far below that possiblewith the ordinary system of control, in addition to which it will benoted that any desired speed of the armature can be secured simply byvarying the speed at which the field-frame is allowed to turn, such variation being secured by changing the position of the operating-arm 17 soas to cause the brake-shoes to bear with more or less force on thebraking-surface.

From the above it will be seen that my improved construction isespecially adapted for use with alternating-current motors of thesynchronous type, for, as it will be understood by those skilled in theart, such motors may be thereby operated in a simple manner so as tosecure any desired speed, since as long as the necessary relative speedis maintained between the two reactive elements of the motor (thearmature and field) it is immaterial whether the field is rotating orfixed.

It will be understood that all heat produced by friction of thebrake-shoes upon the brak ing-surfaceb will be quickly dissipated by therevolution of the field-frame, although this latter may, if desired, beprovided with projecting vanes having any desired surface foraccelerating such cooling. The braking-face Z) is preferably made ofchilled iron, while the braking-shoes b are of wood, these forming thewearing parts of the device and being cheaply and easily renewed.

It is to be understood that I do not confine myself to theparticulararrangement and construction of parts shown, since it isevident that further modifications would be involved, as will beappreciated by those skilled in the art, in adapting various forms ofmotors for operation according to my invention.

While in the foregoing description I have referred to the armature asbeing operatively connected to the load and to the field-frame asrevolving when current is first supplied to the motor, it is to beunderstood that it is immaterial whether such arrangement is literallyfollowed or whether the load is attached to the field-frame, so as toleave the armature, with its suitably-designed braking-surface, free torotate when the current-supply circuit is first closed.

I claim as my invention- 1. In an electric motor, the combination of aframe, two reactive elements supported thereby, one of said elementshaving tubular extensions journaled in said frame, the second of saidelements being carried on a shaft held in said extensions of the firstmember, with means for retarding to any desired extent the speed ofrotation of one of the members, substantially as described.

2. The combination with an electric motor constructed so that it may bestarted without load, of means for causing said motor to assume a load,with a switch controlling the flow of current to the motor and operatedby said means, substantially as described.

3. The combination with an electric motor having a frame and twocoactive elements supported thereby so as to be free to rotate, of anoperating-arm, means connected thereto constructed to vary the speed ofrevolution of one of the members when said arm is moved and an electricswitch also operated by movement of said arm, substantially asdescribed.

4. The combination in an electric motor, of a frame, two reactiveelements supported thereby so as to be free to rotate, means forretarding revolution of one of said elements, an operating-lever havingmeans for causing current to be applied to the motor and constructed tocause operation of said retarding means while permitting said current toflow, substantially as described.

5. The combination in an electric motor, of a frame, two reactiveelements supported thereby so as to be free to rotate, a brakingsurfaceon one of said elements, braking means coacting with said surface, anoperating-lever having means for causing current to be supplied to themotor, said lever being connected to the braking means,substantially asdescribed.

6. The combination in an electric motor, of a frame, two reactiveelements supported thereby so as to be free to rotate, contactpiecesconnected to a source of supply and to an electric motor, anoperating-arm having means coacting with said contact-pieces for causingcurrent to be supplied to the motor, a brake constructed to retard therevolution of one of the elements of the motor, and means connectingsaid operating-arm with the brake, substantially as described.

7. The combination with an electric motor having two rotatable reactiveelements, of two series of contact-pieces connected to a source ofcurrent-supply and to said motor, an operating-lever having meansconstructed to coact with said series of contact-pieces, and a brakeacting upon one of the elements of the electric motor, having meansconnecting it to the operating-lever whereby it is applied by motion ofthe operating-lever irrespective of the particular series ofcontact-pieces in service, substantially as described.

8. An electric motor having two reactive elements of which one isprovided with a braking-surface, a lever pivoted to the frame of themotor and carrying a shoe for engagement with said surface, a switch forsupplying current to the motor, and means connecting the switch to thelever whereby the shoe is caused to bear upon the braking-surfacesimultaneously with the closing' of the switch, substantially asdescribed.

9. An electric motor having rotative reacting elements, levers pivotedto the frame having braking-shoes constructed to bear upon one of theelements, means connecting said levers, a switch, including anoperating-arm, for supplying current to the motor and means forconnecting said levers to said operatingarm, substantially as described.

10. An electric motor having two rotative elements, a brake forretarding the rotation of one of said elements, an operating-arm foractuating said brake, a contact-piece carried by said arm,andcontact-segments electrically connected to the motor constructed topermit motion of the arm without breaking the motor-circuit, whereby thebrake may be applied to the rotating element to any desired extentWithout interrupting the flow of cur rent of the motor, substantially asdescribed.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

, ARTHUR C. EASTWOOD.

Witnesses:

C. W. OoMsTooK, J. E. WELLMAN.

